As a Pagan, I have lived my life interacting with people of other faiths. As a minority religion, I feel that we are often more aware of the religious differences around us that people who follow a more mainstream belief system. I know that most people I pass on the street don't share my beliefs and most likely if the topic of religion comes up, it will be with the assumption that I am Christian.
I am pretty secure in my faith. I had the discussion with my parents about my beliefs when I was in College. My husband has known what path I follow since we met. I don't go out of my way to either hide or share my faith. Who I tell and how much I tell them really depends on what type of relationship we have.
With strangers, I have no need to get into any lengthy discussion about faith. I am not offended when people assume I am Christian. I have no problems with discussing faith in terms that we can all understand. The area I am in is definitely Christian by majority, and if I am just chatting with someone while in a waiting room or line, I don't feel like I need to get into the differences between what I believe and what they believe. I really don't feel like total strangers need to know about this aspect of my life. I can share stories of how blessed I feel or how divinity has touched my life, and have never gotten a strange look at my phrasing. My personal belief is that we each walk a slightly different path anyways, no matter how similar our beliefs might be. But under it all, I think that feeling we feel when we connect with the divine can also connect us to each other.
My husband isn't Pagan. In fact, he is an atheist. I know that he doesn't share the bulk of my beliefs, and some he finds somewhat incomprehensible. However, I also know that he loves me, and that he supports my right to believe in and practice the things I believe in. Our relationship works because we both acknowledge the other as different from ourselves. He likes things I don't care for, and we both have interests the other doesn't share.
Being in an intimate relationship with someone who doesn't share your beliefs can be challenging. I have dated people in the past who were very much aligned with my own practices. A lot of things were easier. But I don't think that hard means impossible.
I think that the keys to making an interfaith relationship work are both communication and balance. There are things I do that I have to explain to my husband, where I wouldn't have to explain it to another Pagan. There are also things that I would explain in much more detail to another Pagan. I don't 'talk shop' as it were with my husband.
Being married to a non-Pagan does effect my practice. While I do have a lot of my practice out in the open, there are some things that I might do if I were on my own that I don't do. I don't feel this is any different than other compromises I make in my life as a married person. Because I have more free time than my husband, I try to organize my life so that when he is home, I am free to do things with him and the things that he isn't interested in I do when he is not here. But I also know that if there are rituals or meditation that I feel I need to do at particular times, then all I have to do is tell him that I will be doing something and ask not to be disturbed.
The majority of my extended family isn't aware of my beliefs. Though my parents do know, they aren't really comfortable with the things I believe (though they have never given me any grief over it). When I visit with my family, my practice is much more subtle than it would be at home. I have never felt right making other people uncomfortable in their own homes. If I am a guest, even with family, I try to be respectful of their beliefs. I don't bring candles and incense with me when I visit them. I still do most of the same daily things I do at home.
In a lot of ways, my daily practice isn't very flashy, so it is easy for me to do things without being overt. I place a lot of weight on intentions. When I look at my life, my actions and how I relate to the other people in my life, I look more at why I do the things I do than what I am doing. If I find that I am not doing something because I am embarrassed to do it in front of other people, then I often stop and really think about why I feel this way. I am pretty stubborn, so if my first response is to hide, my next response is often to go ahead and do it anyways. On the other hand, if I find that my motivation for doing something is to draw attention, then I try to figure out why I think I need that attention. Sometimes the thing I was going to do isn't the healthiest way for me to get the attention I need.
One thing I find somewhat frustrating is the idea that keeping things to myself is somehow detrimental to the Pagan community. I have seen it stated before that not 'being fully out' is one of the causes of the general public not understanding and accepting Paganism. I am not a supporter of the idea that every Pagan must be out in all aspects of their life. To me, the choice on who to tell and how much to tell them is a personal one that we each must make on our own. And often those who think we should all be out, also think we should be kind of loud about our beliefs, standing on a soapbox and proclaiming for all to hear all of the things we believe. Not only that but I think that forcing people to be out is not right, I think that being too pushy about sharing borders on proselytizing. If I don't want random people knocking on my door and telling me about their church, they probably don't want me spouting out my entire religious viewpoint while standing behind them in line for a coffee.
I don't think there is a blanket answer to how to handle interfaith relationships. I think we each need to look at each of our relationships and see what works and what doesn't. I don't think that keeping some things private is always a bad thing. I don't think it is deceitful to avoid full disclosure, especially to people who aren't necessarily close to us. I try very hard to not flat out lie, even to strangers, but I am pretty good at giving my own truths in words that speak to the listener. I fully believe that some people do not want to hear anyone's truth but their own, and I don't feel the need to frustrate myself by trying to change that. If someone is open to discussion and interested in actually learning about me I am more than happy to talk about pretty much anything to anybody.